Isolating specific cell types is often desirable for clinical diagnostic and therapeutic applications. In the clinical diagnostics field, there is a need, for example, for morphological analysis of tumor cells, fetal karyotyping, and tissue typing procedures. Therapeutically, there is a need, for example, for purging cells or tissues intended for use in autologous cellular or tissue transfusions or transplantations, e.g. purging tissues of viral antigens and tumor cells. There is also a need for enriching or isolating desirable cells for use in transplantations, e.g. for use in ex vivo expansion of hematopoietic cells intended for allogeneic and autologous transplantation, and for the use in adoptive immunotherapy of potent antigen presenting cells (dendritic cells), cytotoxic T lymphocytes, natural killer (NK) cells and natural suppressor cells.
Several methods are known in the art for separating desirable cells from body fluids. Such methods include separating cells based upon buoyant density in a cell separation composition (U.S. Pat. No. 4,927,750), separating serological factors on density gradients using latex beads coated with antiserological factor (U.S. Pat. No. 3,862,303), separating cells through the use of a magnetic field (U.S. Pat. No. 4,777,145), and separating T and B cells on density gradients (U.S. Pat. No. 4,511,662). Cell separation methods known in the art may have the disadvantage of cell loss due to the sticking of cells to tubes and pipettes.
There is need for rapid and efficient means of isolating relatively rare populations of cells for diagnostic and therapeutic procedures. The present invention fills this need by providing methods of isolating or enriching minor populations of desirable cells from cell sources or mixtures containing multiple cell populations. Moreover, the invention provides for collection of enriched cells in a high yield.
Specifically, it is the discovery of the present invention that by providing highly defined cell separation media having precisely measured specific densities, specific, defined populations of cells can be isolated and/or depleted. Moreover, the invention provides a cell-trap centrifugation apparatus that greatly enhances collection and allows the automation of this process. Alternatively or in addition, the process is enhanced by use of a density adjusted cell sorting (DACS) step to provide a higher level of specificity to the separation process. The invention also provides specific methods for isolation of specific cell types that are important in diagnostic and therapeutic methods--including fetal nucleated cells, hematopoietic progenitor (CD34.sup.+) cells, selected tumor cells, dendritic cells, NK cells, cytotoxic T-lymphocyte (CTL) and natural suppressor cells. The invention also provides for the depletion of cell types that may interfere with a particular clinical outcome--including, in some cases CTL.